338 On a new Australian Species o/" Thyrsites. of a body-cavity, which are of the utmost value. He adopts a more detailed nomenclature than I have used here, and does not take the same view of the water-vascular system of flat-worms as I have done ; but to some extent there is naturally coincidence, due to the fact that the material here used in the form of facts has been mainly drawn from his other writings and those of other German and Russian embryologists. I have not attempted to discuss Professor Hackel's views nor referred to his terms, chiefly because the substance of this paper was drawn up before the ' Kalkschwamme ' appeared. XXXVI. — On a new Australian Species 0/ Thyrsites. By Prof. Frederick M'Coy. The common Barracoota of the Cape seas is very abundant in the Melbourne market from the adjacent coast, and has long been known ; but an equally large and important species for food is brought in great quantities from Tasmania to the Melbourne fish-shops, usually split open and dried ; and, as far as I can see, it has been overlooked by naturalists. It is easily distinguished at a glance from the Thyrsites atun or Barracoota by the much greater depth of the body, fewer finlets, shorter dorsal, larger teeth, and double lateral line ; but the mode of preparation usually obscures the still more striking character of the ventrals being almost absent, or at least very minute and rudimentary. I subjoin a description of the species. Thyrsites micropus (M'Coy). D. 17 I 4-M2 1 VI. A. 2 + 11. IV. V. 1 -f-1 (bifurcate). P. 14. C. 22f . Height of body five times in total length to centre of caudal fin ; head four times to end of lobes of caudal. Lower jaw projecting in advance of the upper ; diameter of orbit one fifth the length of the head, and one half the length of the muzzle. Ventrals each with one spine and one bifurcate ray, slightly in advance of base of pectorals ; about one third the diameter of the eye in length. Lateral line bifurcate : upper branch ex-tending from a little above the operculum, a little below the dorsal line, as far as the third finlet ; lower branch coming off from upper one under base of fifth dorsal spine, and descending with an abrupt curve nearly to the middle of the side, con-tinuing nearly straight to opposite middle of anal fin, from which to middle of tail it describes three upward undulations.